1. Field of the Disclosure
This application generally relates to recovering from unexpected removal of a flash drive from a computer system, and related matters.
2. Background of the Disclosure
“Flash memory” is a commonly used term for non-volatile data storage that can be read and written multiple times. Flash memory is often used in USB flash drives, sometimes called “flash drives”, which are devices including memory which can communicate with a computer system using a universal serial bus (USB) protocol. Flash drives can often maintain relatively large amounts of data, often sufficiently large that operating system software and a suite of application program software can be maintained in the flash memory. Moreover, most flash drives are sufficiently small that they can draw their power requirements from the computer system to which they are connected.
One consequence of being able to store such relatively large amounts of data is that flash drives might be used to maintain an entire operating environment, including both operating system software and application software, as well as documents or other data in use or saved by a user. An operating environment which can be carried about, often on a key ring or in a pocket, is sometimes called a “portable operating environment”. For example, one such environment is the “Windows to Go”™ environment promoted by Microsoft Corporation of Redmond, Wash. A first advantage of a portable operating environment is that a user can maintain an entire set of settings for personalized use on any available computer system. A second advantage of a portable operating environment is that a user can conduct their computer processing on any available computer system, without leaving personal or otherwise sensitive data for later review by unauthorized persons.
While portable operating environments have several advantages, they are subject to the disadvantage that they might be lost or stolen, as the flash drive which maintains the program and data storage is itself physically small enough to be relatively easily concealed or forgotten. Because of this, some flash drives include a security element, which prevents access to programs and data stored on the flash drive without proof of authorization. The security element might take control when the flash drive is first powered-on, such as when it is coupled to a computer system, and require proof of authorization before allowing that computer system to conduct read or write operations.
While this might achieve the general purpose of protecting the user's programs and data from unauthorized access, it has the drawback that if the flash drive is unexpectedly (such as accidentally or by mistake) removed from the computer system, the flash drive will lose power, reset its state, and the user will lose whatever work was being conducted when the unexpected removal occurred. For example, loss of access to the flash drive can cause the computer system to incur a crash of its operating system, with a possible loss of important user data. A similar problem can occur if the computer system, such as a laptop operating on battery power, enters a power-saving mode and stops supplying power to the flash drive.
One possibility would be to incorporate a battery or a relatively large capacitor into the flash drive, which would preserve the flash drive's state until it could be reinserted into the computer system or until the user could trigger an exit to the power-saving mode. While this possibility might achieve the general purpose of preserving the flash drive's state upon loss of power, it would be subject to additional cost and size for the flash drive, and the reduced security of the possibility that an active portable environment could be moved from one (authorized) computer system to another (unauthorized) computer system.
One possibility would be for the computer system to pause its operations when the flash drive is unexpectedly removed, such as suggested for the “Windows to Go”™ environment described above. While this possibility might achieve the general purpose of preserving the computer system's state when the flash drive is unexpectedly removed, it would be subject to the drawback that flash drives which require a login operation on startup would be in a different state than expected by the computer system, and vice versa. The flash drive would expect the computer system to attempt authorization, while the computer system would expect the flash drive to continue operation. A conflict of state between the two might incur a crash of the computer system, with a possible loss of important user data.
Each of these examples, as well as other possible considerations, can cause difficulty in a portable operating environment, particularly when reliability and security of that portable operating environment are important to the user. For example, the user should take care that the flash memory device does not lose power, such as by specially protecting the flash memory device against accidental removal, providing an additional power source, or disabling the computer system's power-saving modes. Moreover, the user should take care to save their partial results frequently, possibly drawing on the read/write abilities of the flash memory device, possibly interrupting the user's work, and possibly placing additional load on the computer system. Each of these might have a detrimental effect on the value of the computer system and on use of a portable operating environment therewith.